1. Field of the Invention
This invention relates to magnetic hard disk drives.
2. Description of the Prior Art and Related Information
Technological advances and competition in the disk drive industry have benefited both the enterprise and consumers markets by making available ever-higher capacity and performing drives at attractive prices. In some high performance small form factor (e.g., 3.5xe2x80x3 and below) drives where fast data access is critical, the read/write data tracks are limited to a relatively small portion of the disk surface. For example, such disks may have data tracks that occupy only a small portion of the available recordable surface area, such as between the outer edge (or outer diameterxe2x80x94OD) and the middle (or middle diameterxe2x80x94MD) of the disk, for example. Although storage capacity is necessarily sacrificed by limiting the data tracks to a small portion of the available surface area of the disk, the time required for the actuator to swing from the OD of the data tracks to the ID of the data tracks is markedly reduced. In turn, this results in reduced access time, for a given rotational speed of the disk. Such disk drives are commonly called short stroke or de-stroke drives. In some de-stroke drives, the data tracks can occupy, for example, as little as one third of the available recording surface area of the disk.
When the head stack assembly of a disk drive is in a non-operational position, the read/write heads may be xe2x80x9cparkedxe2x80x9d in a position away from the recording surface of the disk. Such parking position may be located, for example, at the ID of the disk in a contact start stop (CSS) zone. The CSS zone of a disk may be textured to prevent stiction between the slider and the surface of the CSS zone. Alternatively, the slider may be padded, to reduce the contact area of the slider with the CSS zone, thereby also avoiding stiction problems with the CSS zone. Alternatively, a ramp load located at the OD of the disk may be used to load and unload the read/write heads during non-operation of the disk drive. In the case of CSS de-stroke drives, even though the actuator only seeks from OD to near MD (or the inner most data track) of the disk during read/write operations, the actuator heads park at the ID of the disk when the drive is turned off or in sleep mode. To park, therefore, the heads must travel the full distance from their current position over the data tracks between OD and MD to the CSS zone adjacent the ID of the disk. The actuators of de-stroke drives, therefore, are conventionally designed with a VCM having a conventional coil angle (i.e., the angle defined by the radial legs of the coil windings of the VCM) and a conventionally sized VCM magnet having two magnetic poles. However, in the case of de-stroke disk drives, the size, structure and mode of operation of conventional actuator assemblies and VCMs have been found to be non-optimal.
What are needed, therefore, are actuators and VCMs that are specifically configured for optimal use in de-stroke drives. What are also needed are high performance de-stroke disk drives containing such specifically configured actuators and VCMs.
This invention can be regarded as a disk drive, including a disk having a recording surface, the recording surface defining a data portion; a head stack assembly including an actuator body; an actuator arm cantilevered from the actuator body; a head coupled to the actuator arm for reading from and writing to the data portion; a coil cantilevered from the actuator body in an opposite direction from the actuator arm, the coil defining a first radial leg and a second radial leg; and a VCM magnet disposed away from the coil so as to define an air gap, the VCM magnet defining a first section, a second section and a third section, the second section being magnetically polarized in an axial direction that is opposite to an axial direction of magnetic polarization of the first and third sections. The first radial leg faces the second section and the second radial leg faces the third section across the air gap when the head is positioned at a predetermined non-operational position over the disk. The first radial leg faces the first section and the second radial leg faces the second section across the air gap when the head is reading from or writing to the data portion.
The predetermined non-operational position may be located within a contact start stop (CSS) area of the disk. Alternatively, the predetermined non-operational position may be located away from the disk and adjacent to an outer diameter of the disk. The data portion defined on the recording surface of the disk may be bounded by the outer diameter of the disk and a medial diameter of the disk. A first magnetic polarity transition zone may be defined between the first and second sections and a second magnetic polarity transition zone may be defined between the second and third sections. The disk drive may be configured to reverse the polarity of the current applied to the coil as the first radial leg passes over the first magnetic polarity transition zone and the second radial leg passes over the second magnetic polarity transition zone. The disk drive may also include a bias force applier, the bias force applier being configured to apply a force that biases the head stack assembly in a bias direction. The bias force may be directed toward the outer diameter of the disk. Alternatively, the bias force may be directed toward the inner diameter of the disk.
According to another embodiment thereof, the present invention is a disk drive, comprising a disk having a recording surface, the recording surface defining a data portion; a head stack assembly including an actuator body; an actuator arm cantilevered from the actuator body; a head coupled to the actuator arm for reading from and writing to the data portion; a coil cantilevered from the actuator body in an opposite direction from the actuator arm, the coil defining a first radial leg and a second radial leg; and a VCM magnet disposed away from the coil so as to define an air gap, the VCM magnet defining a first section and a second section, the first section being magnetically polarized in an axial direction that is opposite to an axial direction of magnetic polarization of the second section. The first and second radial legs respectively face the first and the second sections across the air gap when the head is positioned over the data portion and only the first radial leg faces the second section when the head is at a predetermined non-operational position over the disk.
The predetermined non-operational position may be located within a contact start stop (CSS) area of the disk. Alternatively, the predetermined non-operational position may be located away from the disk and adjacent to an outer diameter of the disk. The data portion defined on the recording surface of the disk may be bounded by the outer diameter of the disk and a medial diameter of the disk. The disk drive preferably also includes a bias force applier, the bias force applier being configured to apply a force that biases the head stack assembly in a bias direction. The bias force may be directed toward the inner diameter of the disk or may be directed toward the outer diameter of the disk.